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Effect of lipid on the conformation of the N-terminal region of equinatoxin II: a synchrotron radiation circular dichroism spectroscopic study

Drechsler, A. and Miles, Andrew J. and Norton, R.S. and Wallace, Bonnie A. and Separovic, F. (2009) Effect of lipid on the conformation of the N-terminal region of equinatoxin II: a synchrotron radiation circular dichroism spectroscopic study. European Biophysics Journal with Biophysics letters 39 (1), pp. 121-127. ISSN 0175-7571.

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Official URL: http://dx.doi.org/10.1007/s00249-009-0445-x

Abstract

Equinatoxin II (EqtII) is a protein toxin that lyses both red blood cells and artificial membranes. Lysis is dependent on the lipid composition, with small unilamellar vesicles (SUVs) of dimyristoylphosphatidylcholine (DMPC) and sphingomyelin (SM) (1:1 molar) being lysed more readily than those of phosphatidylcholine alone. Removing the N-terminus of EqtII prevents pore formation, but does not prevent membrane binding. A peptide corresponding to residues 1–32 of EqtII was found using NMR to adopt a helical structure in micelles. To further understand the structural changes that accompany membrane insertion, synchrotron radiation circular dichroism spectra of the N-terminal peptide in a range of model membranes have been analysed. The peptide structure was examined in water, dodecylphosphocholine (DPC) and DPC:SM (5:1) micelles, and SUVs composed of dioleoylphosphatidylcholine (DOPC) or DMPC, together with SM and cholesterol (Chol). The peptide adopted different conformations in different lipids. Although the presence of SM did not affect the conformation in micelles, inclusion of SM in the bilayer-forming lipid increased the helicity of the peptide. This effect was abolished when Chol was added in DOPC but not in DMPC, which may relate to liquid ordered versus disordered phase properties of the lipid. SM may act as a promoter of membrane organisation necessary for membrane lysis by EqtII.

Item Type: Article
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Biological Sciences
Depositing User: Administrator
Date Deposited: 04 Aug 2010 14:09
Last Modified: 17 Apr 2013 12:17
URI: http://eprints.bbk.ac.uk/id/eprint/1197

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